This invention relates to the use of cocatalysts to enhance the production of particular isomers when di and tri-substituted benzenes are chlorinated. In particular, it relates to the use of cocatalysts to increase the ratio of 3,4-dichlorotoluene (34DCT) to 2,4-dichlorotoluene (24DCT) when parachlorotoluene (PCT) is chlorinated.
34DCT and 24DCT are useful as intermediates in making chemicals such as pharmaceuticals, herbicides, fungicides, insecticides, paint pigments, and polymerization initiators. A mixture of the two isomers can be made without the presence of other DCT isomers by chlorinating pure PCT. The two isomers can then be separated by distillation. Depending upon the particular product being made, it is often desirable to make more of one of the two isomers and less of the other.